Investigation of structural behavior of precast concrete pipe with single elliptical steel cage reinforcement

Abstract

Reinforced Concrete Pipe (RCP) with single elliptical (SE) reinforcement offers cost savings and is permitted by Canadian and American standards. Yet, its use has not yet gained momentum primarily due to limited knowledge of its structural performance. This study explores the structural behavior of full-scale 1050 mm and 1200 mm diameter RCP reinforced with SE cold drawn steel wire cage under the three-edge bearing test. Experimental results show that, given similar amount of reinforcing steel at the tension zone of the inner face of the invert and obvert of the pipe, RCP with SE reinforcing cage meets lower equivalent class than that of RCP with conventional double reinforcing cage. The absence of a second layer of reinforcement in the SE pipes produced more brittle failure characterized by radial tension, followed by concrete slabbing. Increasing the steel reinforcement ratio improved the 0.3-mm crack load and ultimate load capacity up to a certain threshold, beyond which adding more steel did not enhance the results. Results indicate that RCP with SE reinforcement designed per current standards did not meet the specified 0.3-mm crack and ultimate load capacity. Hence, pertinent provisions in CSA A257.2 and ASTM C76 for RCP need to be updated with specific and more suitable guidance for single elliptical cage RCP.